Phillipe Makes a good point about the relationship between heat and retarded timing. I picked up an old Poly 318 truck real cheap because it was overheating and the guy had even cracked the exhaust manifold. After I got it home I didn't like the way it idled and was playing with the carb when I decided to move to the distributor. It was way off and the guy had run it like that for a long time, eventually destroying the exhaust manifolds. What I thought would be a junk motor was simply ignition timing. This old 318 runs great now. My 354 has also showed temperature change with timing changes of less than 4 degrees. I know its not OEM but those electronic conversions from MPP do make the old ones run better. Brian [Non-text portions of this message have been removed]